This invention relates generally to printed wiring board inspection systems, and, more particularly to a printed wiring board inspection and information system which incorporates therein two active inspections in the form of a combined thermal and an ultrasonic testing station, a passive inspection in the form of a video or visual display, and an information station setting forth data relating to printed wiring board identification as well as repair records, and the like.
Printed wiring boards, or in some cases known as printed circuit boards, have recently found its way into use in almost every electronic system. One such use is the electronic network of, for example, aircraft. As is quite readily apparent any intermittent operation or failure of such printed circuit boards or printed wiring boards in an aircraft can be degrading to the mission, or, at the least require extensive effort, that is a distraction to the pilot, to overcome problems encountered as a result of the defectiveness of such boards.
In many instances, an intermittent defect cannot be isolated during ground and shop testing. Therefore, the printed circuit board is generally reinstalled on an operational aircraft for subsequent use. When a printed circuit board shows repeated malfunction in the air but not in ground testing, it is returned to a depot for complete overhaul. At the depot, it is still possible for the printed circuit board to pass both functional, electrical and mechanical testing without isolating the marginal solder connections used therein.
Current depot level quality assurance techniques utilize mainly visual and mechanical methods to insure the physical integrity of solder joints of microelectronic circuits. Therefore, these cracked solder joints can be inspected only in the vertical plane and hidden defects such as voids between the lead and pad, foreign inclusions such as dirt, oil and flux, and internal cracks cannot be detected. Even the less complex assemblies have more than 150 densely packed joints requiring inspection. The more complex assemblies have over 1,000 joints. As mentioned above the existing techniques do not find many hidden defects and so an extremely high percentage of joints on a printed circuit board are marginal and will progress to failure.
In recent years, two tests have been developed which are able to reduce the amount of printed circuit board or printed wiring board failures. Such tests are set forth in the following U.S. Pat. Nos. 3,803,413 and 4,218,922. An even more recent technique is discussed in Laser Focus, vol. 16, no. 6, June 1980, pg. 42.
Unfortunately, reliance on such tests in and by themselves leave much to be desired. First of all each test although effective to some degree, still fails to accurately, by itself, detect all flaws within the printed circuit or wiring board. Therefore, it is highly desirable to provide a system which is capable of providing highly accurate printed wiring board inspection. In addition, once this inspection is complete it would be even more desirable to have a substantially instantaneous analysis of this inspection as well as additional real time information of wiring board history and identification. In addition, it would be even more desirable to combine with inspections fast, accurate, and comprehensive automatic work logging. This would eliminate slow inaccurate and manual work logging of each repaired or reworked content of printed wiring boards.